どういたしまして。

Dōitashimashite.

You’re welcome.

Word for word

“How could I have done anything?”

Politeness: Polite

です/ます style. The safe default with strangers, shop staff and colleagues.

When you would say it

Replying to a thank you.

Worth knowing

Real speakers often reply いえいえ instead; どういたしまして can sound a little stiff.